Pure-tone lateralization revisited

In certain conditions, especially with diotic headphone presentation, hearing sensations are located inside the head. Dichotic headphone presentation can result in lateralization: delaying one of the headphone input signals or reducing its amplitude typically pushes the hearing sensation inside the head towards the contralateral ear. Systematic connections between physical stimulus parameters and hearing-sensation positions provide insight into auditory-localization mechanisms and are helpful in designing and evaluating models. However, typical paradigms of addressing lateral displacement, magnitude estimation or pointing, may suffer from response biases. This study aims at evaluating the suitability of a two-alternative forced choice paradigm: eight normal-hearing subjects were asked to indicate, by pushing one of two buttons, whether the hearing sensation associated with a pure interaural phase or intensity difference occurred "left or right", without any reference or further instructions. Posing a notably simple task without internal mapping, this procedure appears advantageous regarding response biases. The results indicate a high intra-individual reproducibility and plausible inter-individual agreement. None of the participants encountered or reported difficulties using the inherently assumed "internal center" in their decision process. The data suggests the existence of an inter-individually similar decision criterion. Descriptively speaking, the results support the existence of a similar lateralization midpoint.